1. Field of the Invention
The present invention generally relates to devices and methods for highway and traffic engineering data acquisition, including vehicle weighing, vehicle classification, structural analysis, and roadway structural condition monitoring.
2. Background Information
There has long been a need to use electronic sensing in relation to vehicle travel, and obtaining other highway and traffic data for engineering purposes. Current proprietary engineering data acquisition systems for use at permanent roadway sites have been shown to be expensive to install, of limited durability, and for the most part are not interchangeable between the various manufacturers. Current systems require that a large slot be cut into the pavement, and in many cases, that the transducer system be epoxied flush with the surface of the roadway structure. This requires a large expenditure of resources for a relatively short-lived system.
Due to roadway rutting and point impact loading from studded vehicle tires, the durability of these engineering data acquisition systems has been shown to be on the order of two to three years before failure. Many are inherently open loop gain systems, and are subject to an immediate change in calibration. Each axle event has been shown to make a slight change in the characteristics of their transducers. This drift has been demonstrated to be cumulative.
Devices have been patented for obtaining a weight for vehicles while they are in motion. Devices also exist for detecting the presence of a vehicle, in order to activate a traffic signal. Devices also exist for determining the velocity of a vehicle traveling over a certain stretch of road. What these systems lack is the ability to identify a vehicle by the pattern of force which is transmitted by the mass of the vehicle into the roadway structure as the vehicle travels. These prior art systems also lack the ability to analyze the force distribution a vehicle presents to the roadway structure in order to evaluate the loading of each axle of the vehicle, the velocity of a vehicle, and the acceleration and deceleration of a vehicle. These prior art systems also lack the ability to monitor a section of roadway to evaluate the structural condition of the roadway itself. The prior art devices also lack the ability to monitor force distribution from objects and events other than vehicles, such as the force patterns made over road surfaces by avalanches, mud slides, rock falls and even the passage of bicycles, pedestrians and animals. The prior art devices also lack the ability to utilize force distribution from objects and events to track objects and events from one location to another.
Accordingly, it is an object of the invention to provide an apparatus and method for determining the mass, velocity, presence, the acceleration and deceleration, and the tracking of a vehicle over a roadway.
Another object of the invention is to provide an apparatus and method of identifying a vehicle by the force pattern distribution it creates as it passes over a roadway.
A further object of the invention is to provide an apparatus and method for monitoring the physical integrity and condition of a section of roadway structure.
Another object is to provide an apparatus and method for evaluating the distribution of the mass on the axles of a vehicle in motion.
A further object of the invention is to provide an apparatus and a method for detecting the passage of bicycles, pedestrians and animals across a road surface.
A further object of the invention is to provide an apparatus and a method for detecting the presence and severity of such highway maintenance problems as avalanches, mud slides, and rock slides.
Additional objects, advantages and novel features of the invention will be set forth in part in the description as follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
These and other objects are accomplished by a detection system for generating engineering data which senses internal structural picostrains produced by a force event. The picostrains act on an array of one or more transducers, to generate a signal representative of the force event or a signal with information about the force event. The picostrains of interest to the invention include those generated by a vehicle traveling on a roadway or a structure, or another event which generates a force event on a roadway or structure. These picostrains could be sensed by an array of one or more transducers, which generate a signal representative of the force signature of the vehicle or force generator. In one mode of the preferred embodiment of the invention, the applied force from the vehicle creates a three dimensional zone or spheroid of isobaric pressure gradients under each wheel of a vehicle. As a vehicle travels along a road, the wheels of the vehicle apply pressure to the roadway directly below the vehicle. Other objects can create a force event, such as avalanches, rock slides, mud slides, seismic events, pedestrians, animals, bicycles, or motorcycles. The invention can operate in conjunction with a broad array of transducer types, including strain gauges, fiber optic, piezo-electric strip, and cable, accelerometer, capaticitive strip, or any one of many other technologies which may be made to respond to isobaric pressure gradients and horizontal shear.
One version of the invention includes an array of one or more transducers laid horizontally across a roadbed, which sends a filtered and amplified signal to a computer which generates a unique signature for that vehicle, which was the source of the force event. This system can be described in terms of an orthogonal axis system, in which the roadway is the X axis, and the Y axis is horizontal and is perpendicular to the X axis. The Z axis is vertical, and perpendicular to the plane which contains the X and Y axis. The transducer array is laid in slots in the roadway structure, along the Y axis of the roadway. The slots with the transducer array installed are filled with a material such as epoxy which has a modulus of elasticity which makes the slot with the transducer installed behave as an integral part of the roadway structure.
The force which is applied to the roadway structure by a passing vehicle travels along the X axis, and passes over and through the region of the transducer array. The applied force is referenced to a particular time, or To. The applied force is a pressure wave created by an object such as a vehicle traveling on a road. This pressure forms what could be called a virtual spheroid of deformation beneath the applied force. This could be illustrated as a ball with a side compressed from a pressure applied to one side, with the side opposite showing an equivalent compression due to the reactive forces generated within the structural material. The deformation of this virtual spheroid is proportional to:
Fn approximately=ks
where Fn represents the force applied normal to the surface of the spheroid, and where k represents the volumetric force constant of the deformed material, and where s represents the reactive volumetric displacement about the surface of the spheroid. The zone of increased pressure below the wheels of the vehicle is in an isobaric gradient, in an anisotropic structural material, with the highest pressure area closest to the tire, and lower pressure areas radiating out from the tire.
Along with a zone of isobaric pressure with its pressure gradients, the tire of the vehicle can cause a slight physical displacement of the pavement itself. This physical displacement within the pavement structure resembles a wave which proceeds in front of the wheel, and there is also a wave which follows behind the wheel. As the raised wave in the pavement and the pressure gradient under the vehicle tire pass over the transducer, the two adjacent sides of the transducer rotate differentially in relation to each other. This physical rotation of the two opposite sides of the transducer in relation to each other causes the transducer to pass through the lines of magnetic force which emanate from one portion of the earth""s surface and travel towards another portion of the earth""s surface in an arc. As the transducer differentially cuts across these planetary lines of magnetic force, an electrical signal is generated. The electrical signal is referenced to time and passed through an amplifier. A filter follows the amplifier and discriminates against unwanted signal components of the signal generated by the transducers. The amplified and filtered signals are sent to a computer where they are analyzed and stored. A mathematical means within the computer is used to develop a xe2x80x9cproportional kinetic energy envelopexe2x80x9d, or force signature, for the applied dynamic force which generated the signal. This force signature may be represented in a graph which shows pressure, displacement, and time of the signals.
The applied force generated by vehicles is different for each vehicle, and is unique for each vehicle. It is determined by the mass of the vehicle, the distribution of the mass on the wheels, the rolling resistance and other physical characteristics of the tires, the type of suspension of the vehicle, and the adjustment of the suspension.
Due to these differences in mass, tire characteristics, suspension, and tuning of suspension, each vehicle develops a unique pattern of applied force within the pavement structure as it travels. This unique pattern of applied force is what is responsible for the force signature. The transducers of the picostrain detector are displaced by the applied force of the moving vehicle, and send a signal to the computer which interprets the signal to produce a unique signature for each vehicle which passes over the picostrain detector.
Another version of the invention utilizes a transducer which generates a signal due to a change in dimension of the transducer. This can occur if the transducer is configured as a loop around and tightly coupled to a physical structure which expands as a result of a dynamic force applied to it through the center of the transducer loop. The transducer of this version of the invention would be looped around and tightly coupled to a concrete structure, and when a vehicle or other dynamic force generating event passed over the structure, it would expand, as previously explained. This would cause the transducer to also expand, and this change in dimension would generate a signal.
The picostrain detector can in addition detect dynamically applied forces from a number of other force generating events, such as seismic events, motorcycles, bicycles, pedestrians, wheel chairs, railroad equipment, animals, avalanches, mud slides, and rock slides.
These individually unique force signatures for each vehicle can be used in tracking and monitoring vehicles on roadways. A vehicle, such as a semi-tractor trailer rig with a load of goods, can pass over a picostrain detector at the beginning of a trip. At that time, the force signature and an industrial standard identifier for that vehicle and that load is entered into a computer system. As that particular truck passes from state to state and from weigh station to weigh station, it need not stop to be weighed or to have the unique mass distribution applied to each axle checked. Merely by driving over subsequent picostrain detectors, it generates its own force signature, which is compared to the original one on file for that truck with that load. If mass has been added to the truck, such as by adding contraband, or if mass has been removed from the truck, such as by the removal of goods being hauled, the next weigh station would detect this. Similarly, if the trailer was switched to another tractor, or if the axles of the trailer were moved for a different special distribution or configuration and corresponding change in mass over each axle, the next picostrain detector would detect it. At that time, the truck could be pulled over for an inspection. If there were no unusual changes in the force signature for that truck and for said load, it could proceed without stopping to a destination across the country. By comparison, the current practice is for such a vehicle to stop at weigh stations which occur at every border between states, and on a number of highways within the state. At each of these weigh stations, the truck driver has each axle of his truck weighed, and fills out paperwork identifying himself, the truck, and the goods that are on the truck.
In another vehicle tracking application, a gated community or secure facility could utilize picostrain detectors, either alone or in conjunction with detectors of other types, such as but not limited to: human, or video; for gaining admission to the area. All of the vehicles which are authorized to enter the area would pass over a picostrain detector in order to identify the vehicle and to record the force signature for the vehicle. Subsequently, a vehicle which is not authorized to be in that area would be detected, and appropriate steps could be taken to admit or deny access to the vehicle. For instance, in a gated community, a gate could automatically open for all correctly identified vehicles. Vehicles whose force signatures were not pre-approved would have to identify themselves and their reason for entering before being allowed admission. Passing over the picostrain detector would also create a record similar to a sign-in log for every vehicle which passed over it.
Similarly, an automatic processing system for vehicles, passing through a weigh station, a secure, or other facility with multiple decision points in the vehicle processing route, could be implemented.
In another version of the invention, the picostrain detector depends upon the roadway or other structure acting as an isotropic medium, and thus the picostrain detector could evaluate pavement structure for deterioration by noting how well it transmits a known force. When cracks and fissures develop in the pavement, rather than a force being transmitted smoothly through the pavement under the rolling wheels, the force is dissipated into the separate and isolated blocks created by the cracks and fissures in the pavement. Thus, if a known vehicle, type of vehicle, or force signature was identified at a picostrain detector, but its signal became indistinct or diminished over time, the computer could ascertain that the pavement in that region was not transmitting force as an isotropic substance, and that this section of pavement had experienced structural degradation.
Besides evaluating a section of roadway for structural integrity, the picostrain detector could be used to evaluate the structural integrity of other structures, such as concrete bridges, and steel girders.
It could be used in a railroad crossing signal detection system.
In a similar manner, the picostrain detector can be used to detect forces besides vehicles on pavement. For instance, a picostrain detector installed along a section of roadway which is subject to avalanches, would be used to report the presence of an avalanche, the severity and the extent of it. Rock slides and mud slides would be similarly detected and reported. A section of roadway which was particularly prone to avalanching could also have a series of picostrain detectors installed along the section of roadway which would monitor the passages of vehicles. If a particular vehicle was to be detected entering the high avalanche zone, and was not detected exiting the high avalanche zone, and an avalanche occurred at that time, rescuers would know that a vehicle of given classification was possibly trapped in the avalanche, and highway and rescue personnel would know that a vehicle was possibly buried in the avalanche zone as they were using snow removal equipment to clear the highway.
The picostrain detector can include a sensing unit for sensing an applied dynamic force before it reaches the device, determining the range of that applied force, signaling the device for calibration to the proper range, and for resetting the device for repeat operation after that applied force has passed.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein I have shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.